1. Field of the Invention
The present invention relates to embolization particles and a method for making embolization particles.
2. Background of the Invention
Embolization particles are generally particles in an injectable composition that may be introduced or injected into the body via a catheter or other suitable device to form occlusive masses in a selected body region. For example, the composition may be introduced into the human body to block blood flow to portions of malfunctioning human organs, e.g., the kidney, spleen or liver, or to block blood flow into malfunctioning regions of a blood vessel such as arterio-denous malformations (ADM) and aneurysms. The compositions may also be used to occlude vessels providing blood to both malignant and to benign tumors.
There are a variety of materials and devices which have been used for embolization. These include platinum and stainless steel micro-coils, and polyvinyl alcohol particles, including polyvinyl alcohol sponges, to name just a few. In the case of particle or sponge embolization materials, the effectiveness of the particles to form occlusion masses and the precision of placement of these masses depends on the particles tendencies to be dispensed and/or congregated. More specifically, the particles are preferably produced and selected to complement the liquid medium used to carry the particles in the body without plugging or tending to plug the device used to introduce the material into the body. At the same time, however, the particles preferably congregate and pack themselves together once they are delivered to a desired location within the body. Particle shape and consistency is important in predictably balancing these two preferred, yet contradicting functions.
Currently, methods for making embolization particles typically involve forming a block of material, such as for example, a polyvinyl alcohol foam block and bulk shredding the block to form the particles. However, due to the bulk processing of these particles, the respective shapes may vary considerably despite efforts to sort the particles according to their size. FIG. 1 illustrates an example of an embolization particle having a varying shape randomly formed by bulk shredding.
In practice, when an interventionalist selects the embolization particles, she does so typically based on particle size. Her experience regarding the particle size suggests to her how the particles are likely to behave in a given clinic scenario. However, because the shapes of these particles may vary considerably, their performance may also correspondingly vary.